The present invention relates to an inkjet printing head, and more particularly to an inkjet printing head for ejecting the ink by means of piezoelectric devices.
Among non-impact printing methods, the inkjet printing method does not create a noise when printing, prints on normal sheets of paper, and does not require a special setting of the ink, and is therefore considered a method for simple printing accomplished by a simply structured apparatus. Therefore, in the recent years the inkjet printing method has been on the way to its most active development. In the case of this method, a printing head having an ejecting hole is provided for ejecting dyed liquid, to thereby propel droplets thereof. Here, an inlet hole for receiving the liquid is utilized.
Of such inkjet printing heads, the drop-on-demand type printing head for ejecting the ink only upon the signal input, has certain variations. Among these, a Kyser type printing head disclosed in U.S. Pat. No. 3,946,398, is one in that the ink channel is connected to the nozzle, and the piezoelectric device being combined with a bimetal is arranged on one side of the channel, so that the piezoelectric device deforms only when supplied with a voltage. Therefore, liquid ink is even more pressurized in the channel, to ultimately eject the ink through the nozzle. However, such a printing head shows a disadvantage in that the nozzle cannot be fabricated for high-integration due to the size of the piezoelectric device and thus the manufacturing cost rises.
Being different from the Kyser type printing head, the Fischbeck type printing head disclosed in U.S. Pat. No. 4,584,590 is one that utilizes a principle of shear deformation of the piezoelectric device in the electrical field. Here, the piezoelectric device constituting a wall of the channel deforms toward the channel, so that the ink within the channel is forced to be ejected through the nozzle. Such a printing head exhibits a disadvantage in that the nozzle cannot be used for high-integration due to its structural cause.
Another type of printing head, using a shear deformation, is the Bartky type disclosed in U.S. Pat. No. 4,879,568. In this type, the piezoelectric device is arranged parallel to the electrical field for its shear deformation, so that the printing density of the nozzle can be enhanced. However, such a printing head also provides a disadvantage in that the contact portion is easily disrupted due to the tension stress occurring on the contact portion by a deformation (mainly related to the piezoelectric constant) other than shear deformation generated since the manufacture the piezoelectric devices. Moreover, the above printing head has another disadvantage in that the contact portion is easily disrupted by a tension stress thereon, even if the piezoelectric device is combined with an electrode for mass production.